Conventional touch screen computing devices have been configured to identify the positioning and/or movement of one or more fingers or other objects on or near touch surfaces of the devices. For example, certain touch screen computing devices can receive input from a stylus. A stylus is a writing, drawing, or pointing instrument or utensil that is generally configured to be hand held and, in the context of touch screen computing devices, used to interact with a touch surface. For example, touch screen computing devices have identified input based on one end of the stylus moving on or near the touch surface of the computing device. Styli (or styluses) have been used with personal digital assistant devices, tablet computing devices, smart phones, and other touch screen computing devices for handwriting, drawing, selecting icons, and providing other forms of input to such touch computing devices.
There are three general categories of stylus devices: active styli, pressure sensitive styli, and ‘dumb’ styli. Dumb styli have no internal electronic components, no batteries, and typically only have a capacitive rubber tip at an end of a pen-shaped body. Active styli are self-contained systems designed to work with specific, usually proprietary, touch computing devices. Active styli may include radios or other means to communicate with a particular touch device/platform and are typically limited to working with a proprietary touch screen interface of a closed, proprietary system. This is because active styli are typically designed to be used with a particular tablet device. Such active styli are constrained to working with a given platform because other, third party touch computing platforms and devices will not recognize these closed-system styli as valid input devices.
In contrast to active styli, pressure sensitive styli are often designed to work with third party touch screens and touch computing devices not made by the manufacturer of such styli. Example pressure sensitive styli are described in more detail in U.S. patent application Ser. No. 13/572,231 entitled “Multifunctional Stylus”, filed Aug. 10, 2012, which is incorporated by reference herein in its entirety. Pressure sensitive styli may include a wireless transceiver or other means for wirelessly communicating with touch computing devices. Some styli include a light emitting diode (LED) or other means to indicate that the stylus is powered on or communicating with a touch device. Wireless styli with such internal electronics require their own, internal power supply. Prior solutions involved incorporating user-replaceable batteries, such as AAA and AAAA-sized cells, into styli. However, the relatively large size and weight of replaceable batteries result in larger and heavier styli. Use of cylindrical replaceable batteries such as AAA and AAAA cells requires that stylus bodies be wider than traditional writing and drawing instruments, such as pens and pencils, which do not ergonomically enhance their use as styli and may cause discomfort during extended periods of use.
In order to address the size and weight issues implicit in use of traditional replaceable batteries, some styli are powered by relatively smaller, captive batteries. Because such captive batteries are not user-replaceable, these styli must be periodically recharged. Prior solutions for stylus charging include using a wired connection between a stylus and a power supply via a plug, port, or receptacle built into the stylus or including magnetic materials in the stylus so that the stylus can be magnetically coupled to a power supply. Another charging technique for mobile devices is inductive charging using inductive coupling between an inductive charging station and a device having a battery to be charged. Such inductive charging requires inclusion of an induction coil within the device whose battery is being recharged. Some inductive coupling techniques use magnets and magnetic material within a device to be charged to ensure that the device remains in close enough proximity to the charging station to be inductively charged. Each of these charging technologies and techniques have the drawbacks of adding size and weight to the devices being charged, thus making them less aesthetically pleasing and not ergonomically enhancing their use as styli. In addition, incorporating magnetic materials and induction coils into styli can interfere with certain electronic components contained within some styli, such as wireless transceivers.
Styli can be susceptible to damage from mechanical impulse forces, particularly pressure-sensitive styli whose tips include pressure-sensitive elements. Pressure sensitive styli seek to provide many different levels of pressure sensitivity, which can be useful in drawing, graphics, and other touch-based applications. Such pressure sensitivity can be achieved via use of pressure sensitive tips and sensors, which can include relatively small moving parts and sensitive components. Traditional techniques for limiting damage to styli include inserting them into a desktop dock or base, covering their tips with stylus-specific caps, or placing them in a case when not in use. The dual needs for recharging and damage prevention are compounded in mobile environments where a power supply and protective docks or cases may not be readily available.